The existing walking beam pumpjacks are mainly as follows: conventional walking beam pumpjack, pre-posed walking beam pumpjack, bias walking beam pumpjack and unusually shaped walking beam pumpjack, etc, and at present, the walking beam pumpjack generally includes a horsehead, a walking beam, a derrick, a connecting rod, a substructure, a crank, a balance device, a decelerator, a brake, a motor and a beam hanger. With the derrick, decelerator, brake, motor, control cabinet, etc. fixedly mounted on the substructure, the walking beam hinged on the derrick, the crank fixedly mounted on the output shaft of the decelerator, one end of the connecting rod hinged on the crank, and the other end of the connecting rod hinged on the walking beam, a four-connecting-rod-structure is formed. The horsehead is mounted on the front end of the walking beam, and the beam hanger is mounted on the horsehead; the balance device is mounted on the crank, or/and the balance device is mounted on the walking beam, so that the balance is adjusted by varying the balance torque by adding and subtracting the mass of the counterweight manually, or/and by varying the position of the counterweight; however, the existing walking beam pumpjack has significant deficiencies in terms of two aspects: first, the balance cannot be adjusted automatically, and it needs to be adjusted in time based on the variation in oil well load. If the balance rate is very low, the operation state of the pumpjack will deteriorate and the power consumption thereof will increase; second: the frequency of stroke cannot be adjusted automatically, which causes the oil-pumping capacity of the pumpjack to be constantly higher or lower than the oil production. If the pumpjack's frequency of stroke is too high, the oil-pumping capacity will be higher than the oil production of oil well, which in turn causes an empty pumping and liquid impact, damages the pumpjack, the oil-pumping rod, the pump, reduces the service life, and wastes electric energy; if the pumpjack's frequency of stroke is too low, the oil-pumping capacity will be lower than the oil production of oil well, which in turn reduces oil well production.